1. Field of the Invention
The present invention relates to transmit power control in cell phones and the like.
2. Prior Art
Power amplifiers for cell phones work over a wide range of power levels when broadcasting information. The power level is dictated by the base station, and depends on numerous factors. RF couplers and sensors, or sensor/detectors, are used in the feedback loop of RF power amplifiers for gain control. The transfer characteristic of the detector typically used, Vout vs. Pout, where Vout is the output of the sensor and Pout is the output power of the power amplifier, is approximately exponential. However it is highly desirable for the sensor/detector combination to have a linear transfer characteristic over the dynamic range of the power amplifier for the most accurate control of the power amplifier. In the prior art, a single coupler element was used. However, because of the non-linear characteristics of the detector within the dynamic range of interest, compensation electronics was heretofore required to adequately linearize the detector's response.